In recent years, a white LED has been brought to attention as a white lighting light source exhibiting high efficiency as well as high reliability, and has already been utilized partly as a small-size low electric power light source. It is commonly known that this kind of LED is a LED in which a blue LED element is covered by a mixture of a yellow phosphor and a transparent resin, and a white LED and a phosphor used for the white LED with this method are disclosed (refer to Patent Documents 1-3).
However, there are a number of problems to be solved in this method as a light source for back light and general lighting, since no red component is contained in white light obtained in this method. On the other hand, attention has recently been focused on a white light emitting diode utilizing a LED emitting in the UV region because of no drawback as described above. However, a type of diode molded in a conventional resin tends to deteriorate the resin since energy generated via emission is large. Therefore, the resin loses the color by using the white LED having such the structure for long duration, whereby the color tone is also changed. Further, in recent years, though there is a move to introduce the development of a white lighting light source by employing a high-power LED element, the resin is seriously deteriorated in this case since a limited area is exposed to extremely large energy blue light, whereby change of an emission color is caused in an extremely short period of time. There was also a problem such that the emission color tone was changed over time, since a heat discharge property of a resin-molded element is poor, whereby temperature rise is easily generated.
(Patent Document 1) Japanese Patent O.P.I. Publication No. 10-163535
(Patent Document 2) WO98/05078; descriptive literature
(Patent Document 3) Japanese Patent O.P.I. Publication No. 2002-43624